Conventionally, as linear motor actuators, there are known ones disclosed in JP2004-274950 A and JP2004-312983 A. Each of the linear motor actuators disclosed in those publications includes a track rail which has a bottom plate and a pair of side walls and formed into a channel shape therewith, a slide block incorporated between the pair of side walls of the track rail through intermediation of a plurality of balls, and a linear motor for thrusting the slide block along the track rail.
The linear motor includes stator magnets having magnetic poles of N poles and S poles alternately arranged on a straight line, for generating magnetic fields, and a coil member serving as a mover which is electrified by an alternating current to generate a moving magnetic field along an arrangement direction of the magnetic poles of the stator magnets. The stator magnets are provided on the bottom plate along a longitudinal direction of the track rail. The coil member is mounted to the slide block itself or a table fixed to the slide block, and is opposed to the stator magnets through intermediation of a little gap.
There are coil members of types including and not including a core member formed of a ferromagnetic material such as iron. In view of the level of a generated thrust force, the coil member of the former type is advantageous. The core member is provided with teeth, the number of which is a natural-number multiple of the number of phases of the alternating current, and which are opposed to the stator magnets. A coil is wound around each of those teeth. When the coil is energized, each of the teeth becomes an electromagnet. Between each of the teeth and each of the magnetic poles constituting the stator magnets, there is generated a magnetic attractive force or a magnetic repulsive force with respect to each of the magnetic poles. For example, a three-phase alternating current is formed of three alternating currents of u phase, v phase, and w phase differing in phase from each other by 120 degrees. Accordingly, when the alternating currents differing in phase by 120 degrees are successively allowed to pass through the coil wound around the series of teeth such that the tooth at one end of the core member is supplied with the alternating current of the u phase, the teeth next thereto is supplied with the alternating current of the v phase, and the teeth next thereto is supplied with the alternating current of the w phase, there occurs such a phenomenon that the magnetic field looks as if it moves from the tooth positioned at one end of the core member toward the tooth positioned at another end thereof. This is the above-mentioned moving magnetic field. Owing to cooperation between the moving magnetic field and the stator magnets, a thrust force acts between the mover and the stator magnets.    Patent Document 1: JP 2004-274950 A    Patent Document 2: JP 2004-312983 A